The pour point of an oil is defined as the lowest temperature at which the oil will pour or flow when chilled without disturbance under specified conditions. The problems associated with pour point ordinarily have to do with the storage and use of heavy oils such as lubricating oils, but the recent increased use of distillate fuel oils have revealed similar problems even with these lighter, more fluid materials. Pour point problems arise through the formation of solid or semi-solid waxy particles in an oil composition. In the storage of furnace oils or diesel oils during the winter months, for example, temperatures may decrease to a point as low as -15.degree. F. to -25.degree. F. The decreased temperatures often cause crystallization and solidication of wax in the distillate fuel oil. Distribution of heating oils by pumping or siphoning is rendered difficult or impossible when temperatures are around or below the pour point of the oil. Furthermore, at such temperature, the flow of the oil through the filters cannot be maintained, and the result is a failure of the equipment to operate.
This difficulty has been remedied in some instances by using lighter fractions as fuel oils, i.e., by lowering the maximum distillation temperature at which a distillate fraction is cooled. It has also been suggested that the distillate fuel oils be dewaxed such as by urea dewaxing. Separately or in combination, these remedies are, however, economically prohibitive. That is, readjustment of end points causes the loss of valuable blending material for distillate fuel stocks and dewaxing operations are expensive.
Another approach to the problem has involved a search for a pour point depressant which will decrease the pour point of the distillate fuel oil. Unfortunately, pour point depressants which are normally effective in lubricating oils and other heavy oils are generally ineffective in distillate fuel oil. Such pour point depressants are also, in many instances, ineffective in dispersing or suspending wax crystals that form in the fuel oil, and often migrate along with other additives to the bottom of the storage vessel with the wax crystal. This latter problem is particularly true of copolymers of ethylene vinyl acetate under various circumstances.
Ethylene containing copolymer additives for use as pour point depressants for fuel oils are described in U.S. Pat. Nos. 3,037,850; 3,048,479; 3,069,245; 3,093,623; 3,126,364; 3,131,168; 3,159,608; 3,254,063; 3,309,181; 3,341,309; 3,388,977; 3,449,251; 3,565,947; and 3,627,838.
Additive combinations that include ethylene copolymers that are useful as pour point depressant and/or wax suspension or dispersion agents in fuel oils are described in U.S. Pat. Nos, 3,638,349; 3,642,459; 3,658,493; 3,660,058; 3,790,359; 3,955,940; 3,961,916; 3,981,850; 4,087,255; 4,147,520; 4,175,926; 4,211,534; 4,230,811; and 4,261,703.
Hydrocarbyl-substituted carboxylic acylating agents having at least 30 aliphatic carbon atoms in the substituent are known. The use of such carboxylic acylating agents as additives in normally liquid fuels and lubricants is discussed in U.S. Pat. Nos. 3,288,714 and 3,346,354. These acylating agents are also useful as intermediates for preparing additives for use in normally liquid fuels and lubricants as described in U.S. Pat. Nos. 2,892,786; 3,087,936; 3,163,603; 3,172,892; 3,189,544; 3,215,707; 3,219,666; 3,231,587; 3,235,503; 3,272,746; 3,306,907; 3,306,908; 3,331,776; 3,341,542; 3,346,354; 3,374,174; 3,379,515; 3,381,022; 3,413,104; 3,450,715; 3,454,607; 3,455,728; 3,476,686; 3,513,095; 3,523,768; 3,630,904; 3,632,511; 3,697,428; 3,755,169; 3,804,763; 3,836,470; 3,862,981; 3,936,480; 3,948,909; 3,950,341 and French Pat. No. 2,223,415. The preparation of such substituted carboxylic acid acylating agents is known. Typically, such acylating agents are prepared by reacting one or more olefin polymers which contain an average of, for example, from about 30 to about 300 aliphatic carbon atoms, with one or more unsaturated carboxylic acid acylating agents. The use of chlorine in the preparation of such acylating agents has been suggested as a means for improving the conversion of the reaction of olefin polymers and unsaturated carboxylic acid acylating agents. Methods for preparing substituted carboxylic acid acylating agents by this method are disclosed in U.S. Pat. Nos. 3,215,707; 3,219,666; 3,231,587; 3,787,374 and 3,912,764.
Reactions of such substituted carboxylic acylating agent with amines and/or alcohols to form additives for use in fuels and/or lubricants are described in U.S. Pat. Nos. 3,219,666; 3,252,908; 3,255,108; 3,269,946; 3,311,561; 3,364,001; 3,378,494; 3,502,677; 3,658,707; 3,687,644; 3,708,522; 4,097,389; 4,225,447; 4,230,588; and Re. 27,582.
Although many pour point depressant/wax suspension additive systems have been suggested, concerted efforts are constantly being made to find new additives or additive systems which are more economical and more effective than the additives and additive systems known in the art.